Mass airflow sensor and hydrocarbon trap combination

ABSTRACT

A combined mass airflow sensor and hydrocarbon trap is provided for absorbing evaporative hydrocarbon emissions from an air intake duct of an internal combustion engine. The combined mass airflow sensor and hydrocarbon trap comprises a duct that supports a hydrocarbon absorbing sheet in an unfolded configuration within a housing. The duct communicates an airstream from an air filter to the air intake duct during operation of the internal combustion engine. An opening in the housing receives a mass airflow sensor into the duct, such that the mass airflow sensor is disposed within the airstream. Guide vanes extending across the duct reduce air turbulence within the airstream passing by the mass airflow sensor. Ports disposed along the duct allow the evaporative hydrocarbon emissions to be drawn into the interior and arrested by the hydrocarbon absorbing sheet when the internal combustion engine is not operating.

PRIORITY

This application claims the benefit of and priority to U.S. Pat.Application No. 16/823,183 filed Mar. 18, 2020 and U.S. Pat. ApplicationNo. 15/847,746 filed on Dec. 19, 2017 and now issued as U.S. Pat. No.10,598,137 date Mar. 24, 2020 and U.S. Provisional Application, entitled“Mass Airflow Sensor And Hydrocarbon Trap Combination,” filed on Dec.20, 2016 and having application serial number 62/436,989.

FIELD

The field of the present disclosure generally relates to engine airintake systems. More particularly, the field of the invention relates toa combined mass airflow sensor and hydrocarbon trap that exhibits a lowresistance to airflow and absorbs evaporative hydrocarbon emissions froman intake manifold of an internal combustion engine after engineshutdown.

BACKGROUND

An air intake filter removes particulate matter from air entering an airintake manifold of a motor vehicle. A variety of filter shapes haveevolved over time for this purpose, such as flat panel, ring,cylindrical and frustoconical (section of a cone) designs. While airfilters have largely served the purpose of removing particulate matter,such as dirt or debris, from the air entering the air intake manifold,such filters provide little help in preventing evaporative emissionsfrom leaking out of the intake manifold and entering the atmosphere.Such emissions, arising chiefly when the engine is turned off and theintake manifold is hot, are a well-known contributor to air pollution.

During operation of an internal combustion engine, an airflow is drawnthrough the air intake system into an intake manifold and then finallyinto combustion chambers of the engine. The airflow is caused by theintake stroke of pistons within the engine, which forms an internalpressure within the intake manifold that is lower than the atmosphericpressure of the environment, and thus outside air is drawn into the airintake system. Evaporative emissions are prevented from exiting the airintake system due to the low internal pressure within the intakemanifold and the airflow into the air intake system during operation ofthe internal combustion engine.

After engine shut-down, air continues to rush through the air intakesystem until the internal pressure within the intake manifold equals theatmospheric pressure of the environment. Evaporative hydrocarbons may beemitted if un-combusted fuel is present in the air intake system, suchas due to pressurized fuel leaking from fuel rail(s) into the intakemanifold through fuel injectors. This small amount of fuel may vaporize,and the resulting hydrocarbon vapor may migrate out of the air intakesystem into the atmosphere. Although such hydrocarbon vapor egress wasonce considered negligible, current regulations and environmentalawareness have created a desire to eliminate evaporative emissions fromthe air intake systems of internal combustion engines.

Attempts to eliminate evaporative hydrocarbon emissions have includedplacing secondary, hydrocarbon adsorbing filters directly across thepath of airflow into the air intake system. As will be appreciated,however, disposing extra layers of filtration media across the airflowpath causes an additional flow restriction to be placed onto the airintake system. As such, the internal combustion engine is generally lessefficient, or the air intake system may need to be increased in size soas to compensate for the increased flow restriction.

Other attempts to eliminate evaporative hydrocarbon emissions haveincluded combining hydrocarbon vapor-adsorbing materials withconventional air filters. One drawback associated with these combinationfilters includes vapor-adsorbing materials flaking out of thecombination filter and entering the air intake system. Further, such aloss of vapor-adsorbing materials may adversely affect the vaporabsorbance of the combination filter. Accordingly, there is a need foreliminating hydrocarbon leakage from air intake systems of internalcombustion engines without adversely affecting engine performance.

SUMMARY

A hydrocarbon trap is provided for absorbing evaporative hydrocarbonemissions from an air intake duct of an internal combustion engine. Thehydrocarbon trap comprises a duct configured to communicate an airstreamfrom an air filter to the air intake duct. A multiplicity of ports aredisposed along the duct to allow evaporative hydrocarbon emissions to bedrawn from the air intake duct. A housing is configured to support theduct and at least one hydrocarbon absorbing sheet to arrest theevaporative hydrocarbon emissions. The housing is configured to becoupled with an air box so as to communicate the airstream through theduct during operation of the internal combustion engine. The duct iscoupled with at least one support configured to maintain the hydrocarbonabsorbing sheet in an unfolded configuration adjacent to an innerperimeter surface of the housing. A port in the housing is configured tosupport a mass airflow sensor within the duct. At least one guide vaneextends across an interior of the duct adjacent to the mass airflowsensor and is configured to reduce air turbulence within the airstreampassing through the duct during operation of the internal combustionengine.

In an exemplary embodiment, a hydrocarbon trap for absorbing evaporativehydrocarbon emissions from an air intake duct of an internal combustionengine comprises: a duct configured to communicate an airstream from anair filter to the air intake duct; a multiplicity of ports disposedalong the duct to allow evaporative hydrocarbon emissions to be drawnfrom the air intake duct; a housing configured to support the duct andat least one hydrocarbon absorbing sheet to arrest the evaporativehydrocarbon emissions; and a port in the housing configured to support amass airflow sensor within the duct.

In another exemplary embodiment, the duct is coupled with at least onesupport configured to maintain the hydrocarbon absorbing sheet in anunfolded configuration adjacent to an inner perimeter surface of thehousing. In another exemplary embodiment, the at least one support isconfigured with a shape that matches the shape of the interior and asize that provides clearance for the hydrocarbon absorbing sheet to bedisposed between the edges of the at least one support and the innerperimeter surface.

In another exemplary embodiment, the housing is configured to be coupledwith an air box so as to communicate the airstream through the ductduring operation of the internal combustion engine. In another exemplaryembodiment, the housing comprises a mounting surface that is configuredto mate with a substantially similar surface disposed on the air box. Inanother exemplary embodiment, one or more holes disposed in the mountingsurface are configured to receive fasteners for coupling the housing tothe air box.

In another exemplary embodiment, the port is configured to extend themass airflow sensor into the airstream within the duct during operationof the internal combustion engine. In another exemplary embodiment, theduct includes a channel that is configured to receive the mass airflowsensor when the duct is installed into the housing. In another exemplaryembodiment, the hydrocarbon absorbing sheet includes a separationconfigured to receive the mass airflow sensor when the duct is installedinto the housing.

In another exemplary embodiment, at least one guide vane extends acrossan interior of the duct adjacent to the mass airflow sensor and isconfigured to reduce air turbulence within the airstream passing throughthe duct during operation of the internal combustion engine. In anotherexemplary embodiment, the at least one guide vane comprises two guidevanes disposed on opposite sides of the mass airflow sensor andconfigured to encourage a substantially laminar flow of the airstream onboth sides of the mass airflow sensor.

In an exemplary embodiment, a hydrocarbon trap for absorbing evaporativehydrocarbon emissions from an air intake duct of an internal combustionengine comprises: a housing coupled with an air filter; a duct disposedwithin the housing to communicate an airstream from the air filter tothe air intake duct; a hydrocarbon absorbing sheet disposed between theduct and the housing; and a mass airflow sensor disposed within theairstream.

In another exemplary embodiment, the duct is comprised of at least onesupport configured to maintain the hydrocarbon absorbing sheet in anunfolded configuration adjacent to an inner perimeter surface of thehousing. In another exemplary embodiment, a multiplicity of portsdisposed along the duct are configured to allow the evaporativehydrocarbon emissions to be drawn from the air intake duct into thehousing. In another exemplary embodiment, the housing comprises a portconfigured to extend the mass airflow sensor into the duct.

In another exemplary embodiment, at least two guide vanes extend acrossthe duct adj acent to the mass airflow sensor and are configured toreduce air turbulence within the airstream passing by the mass airflowsensor during operation of the internal combustion engine. In anotherexemplary embodiment, the mass airflow sensor is disposed between the atleast two guide vanes, such that the airstream is substantially laminaron both sides of the mass airflow sensor. In another exemplaryembodiment, the housing is configured to be coupled with an air box thatcontains the air filter, such that the airstream is communicated fromthe air filter to the air intake duct.

In an exemplary embodiment, a hydrocarbon trap for absorbing evaporativehydrocarbon emissions from an air intake duct of an internal combustionengine comprises: a duct configured to communicate an airstream from anair filter to the air intake duct; a housing configured to support theduct and at least one hydrocarbon absorbing sheet within an interior ofthe housing; one or more supports coupled with the duct and configuredto maintain the hydrocarbon absorbing sheet in an unfolded configurationwithin the housing; and a multiplicity of ports disposed along the ductand configured to allow the evaporative hydrocarbon emissions to bedrawn from the duct and arrested by the hydrocarbon absorbing sheet.

In another exemplary embodiment, the housing is configured to be coupledwith an air box that at least partially surrounds the air filter, suchthat the airstream is communicated into the duct during operation of theinternal combustion engine. In another exemplary embodiment, the housingcomprises a port configured to receive a mass airflow sensor into theduct, such that the mass airflow sensor is exposed to the airstream.

BRIEF DESCRIPTION OF THE DRAWINGS

The drawings refer to embodiments of the present disclosure in which:

FIG. 1 illustrates an exemplary embodiment of an air box containing anair filter coupled with a combined mass airflow sensor and hydrocarbontrap in accordance with the present disclosure;

FIG. 2 illustrates a first exploded view of an exemplary embodiment of acombined mass airflow sensor and hydrocarbon trap;

FIG. 3 illustrates a second exploded view of the combined mass airflowsensor and hydrocarbon trap of FIG. 1 ;

FIG. 4 illustrates a side plan view of an exemplary embodiment of acombined mass airflow sensor and hydrocarbon trap;

FIG. 5 illustrates a front plan view of the combined mass airflow sensorand hydrocarbon trap of FIG. 4 ;

FIG. 5A illustrates a cross-sectional view of the combined mass airflowsensor and hydrocarbon trap of FIG. 5 , taken along a line A-A;

FIG. 6 illustrates a rear plan view of the combined mass airflow sensorand hydrocarbon trap of FIG. 4 ; and

FIG. 6A illustrates a cross-sectional view of the combined mass airflowsensor and hydrocarbon trap of FIG. 6 , taken along a line B-B.

While the present disclosure is subject to various modifications andalternative forms, specific embodiments thereof have been shown by wayof example in the drawings and will herein be described in detail. Theinvention should be understood to not be limited to the particular formsdisclosed, but on the contrary, the intention is to cover allmodifications, equivalents, and alternatives falling within the spiritand scope of the present disclosure.

DETAILED DESCRIPTION

In the following description, numerous specific details are set forth inorder to provide a thorough understanding of the present disclosure. Itwill be apparent, however, to one of ordinary skill in the art that theinvention disclosed herein may be practiced without these specificdetails. In other instances, specific numeric references such as “firstfilter medium,” may be made. However, the specific numeric referenceshould not be interpreted as a literal sequential order but ratherinterpreted that the “first filter medium” is different than a “secondfilter medium.” Thus, the specific details set forth are merelyexemplary. The specific details may be varied from and still becontemplated to be within the spirit and scope of the presentdisclosure. The term “coupled” is defined as meaning connected eitherdirectly to the component or indirectly to the component through anothercomponent. Further, as used herein, the terms “about,” “approximately,”or “substantially” for any numerical values or ranges indicate asuitable dimensional tolerance that allows the part or collection ofcomponents to function for its intended purpose as described herein.

In general, the present disclosure describes a combined mass airflowsensor and hydrocarbon trap for absorbing evaporative hydrocarbonemissions from an air intake duct of an internal combustion engine. Thecombined mass airflow sensor and hydrocarbon trap comprises a housingthat is configured to support a duct and at least one hydrocarbonabsorbing sheet within an interior of the housing. The duct isconfigured to communicate an airstream from an air filter to the airintake duct during operation of the internal combustion engine. Amounting surface of the housing may be configured to mate with, and befastened to, a substantially similar surface disposed on an air box thatcontains the air filter. The housing comprises a port that is configuredto receive a mass airflow sensor into the duct, such that the massairflow sensor is disposed within the airstream. A pair of guide vanesextend across the duct and are configured to reduce air turbulencewithin the airstream passing adjacent to the mass airflow sensor throughthe duct. At least one support comprising the duct is configured tomaintain the hydrocarbon absorbing sheet in an unfolded configurationadjacent to an inner perimeter surface of the housing. The shape of thesupport matches the shape of the interior, and the support has a sizethat provides clearance for the hydrocarbon absorbing sheet to bedisposed between the edges of the support and the inner perimetersurface. A multiplicity of ports disposed along the duct are configuredto allow the evaporative hydrocarbon emissions to be drawn into theinterior and arrested by the hydrocarbon absorbing sheet when theinternal combustion engine is not operating.

FIG. 1 illustrates an upper perspective view of an exemplary embodimentof a lower portion of an air box 100 that contains an air filter 104coupled with a combined mass airflow sensor and hydrocarbon trap 108(hereinafter, “hydrocarbon trap”) in accordance with the presentdisclosure. The air box 100 is comprised of at least one air inlet 112that communicates an airstream 116 into an interior 120 of the air boxby way of a duct 124. The air filter 104 is disposed within the interior120 and configured to remove particulate matter and contaminants thatmay be flowing with the airstream 116 before the airstream passesthrough the hydrocarbon trap 108 and then is directed through a conduit128 to an air intake duct of the internal combustion engine. Thehydrocarbon trap 108 is configured to absorb evaporative hydrocarbonemissions leaking from the air intake duct when the internal combustionengine is not operating.

The air box 100 generally is comprised of a housing 132 that isconfigured to improve movement of the airstream 116 through the airfilter 104. The housing 132 is configured to support the air filter 104and provide an interface between an interior of the air filter and theair intake duct of the engine. It is contemplated that varioustechniques may be employed to couple the air filter 104 with theinterior 120 of the housing 132, without limitation. For example, thehousing 132 may include a mount portion that facilitates coupling theair filter 104 with an interior surface of the housing, therebyestablishing an air-leak resistant connection between the interior ofthe air filter 104 and the air intake duct of the engine. The housing132 preferably is comprised of a material that is sufficiently durableand temperature resistant to retain its configuration during operationwhen coupled with the air intake duct of the engine. It is envisionedthat the housing 132 may be formed by way of injection molding, or othersimilar techniques.

FIGS. 2-3 illustrate exploded views of an exemplary embodiment of thehydrocarbon trap 108 that may be coupled with the air box 100 accordingto the present disclosure. The hydrocarbon trap 108 is comprised of ahousing 136 that supports a duct 140 and at least one hydrocarbonabsorbing sheet 144 within an interior 148 of the housing. The duct 140is comprised of two or more supports 152 that are configured to maintainthe hydrocarbon absorbing sheet 144 disposed in a smooth, unfoldedconfiguration adjacent to an inner perimeter surface 156 of the housing136. The supports 152 generally have a shape that matches the shape ofthe interior 148, and have a size that provides enough clearance for thehydrocarbon absorbing sheet 144 to be disposed between the edges of thesupports 152 and the inner perimeter surface 156, as shown in FIG. 5A.The supports 152 may be fabricated as extended portions of the duct 140in the form of an individual component, or may be comprised of separatecomponents that may be coupled with the duct 140.

A multiplicity of ports 160 disposed along the duct 140 are configuredto allow evaporative hydrocarbon emissions to be drawn to, and arrestedby the hydrocarbon absorbing sheet 144 when the engine is not operating.As best shown in FIGS. 3 and 6A, the ports 160 may be comprised ofnarrow openings within the duct 140 that allow evaporative hydrocarbonemissions to migrate into the interior 148, between the supports 152. Itshould be understood, however, that the ports 160 are not to be limitedto narrow openings, but rather the ports 160 may be comprised of shapedopenings other than the narrow openings illustrating in FIGS. 3 and 6A.Further, it is envisioned that, in some embodiments, any of variousshaped portions, ridges, channels, ducts, and any other surfacefeatures, may be incorporated into the duct 140 and coupled with theports 160, as is deemed beneficial to the evaporation of hydrocarbonemissions, without limitation.

The duct 140 is configured to direct the airstream 116 through thehydrocarbon trap 108 while the engine is operating. As such, the duct140 comprises a flange 164 that is configured to be coupled with the airfilter 104. The flange 164 may be directly received into a base of theair filter 104, or may be coupled with a tube, duct, or adaptercomprising a portion of the air box 100 that receives the air filter104. Further, the housing 136 comprises a mounting surface 168 andmultiple holes 172 that are configured to enable fastening thehydrocarbon trap 108 onto the air box 100 so as to place the flange 164into fluid communication with the interior of the air filter 104, asdescribed herein. It is contemplated that the mounting surface 168 maybe configured to mate with a substantially similar surface disposed onthe air box 100. A suitable gasket may be positioned between themounting surface 168 and the surface on the air box 100 so as to providean air-leak resistant joint between the air filter 104 and the airintake duct of the engine.

As best shown in FIG. 3 , the housing 136 comprises an opening or port176 that is configured to receive a mass airflow sensor 180 into thehydrocarbon trap 108 such that the mass airflow sensor 180 may be placedinto contact with the airstream 116, as best shown in FIGS. 4, 5, and 6. A channel 184 disposed within the duct 140 and a separation 188comprising the hydrocarbon absorbing sheet 144 are configured toaccommodate the mass airflow sensor 180 extending into the interior 148during installation of the duct 140 and the hydrocarbon absorbing sheet144 into the housing 136. For example, the channel 184 and separation188 may facilitate inserting the duct 140 and hydrocarbon absorbingsheet 144 into the housing 136 after the mass airflow sensor 180 hasbeen inserted into the port 176 and fastened onto the housing 136. It iscontemplated that the channel 184 and separation 188 may facilitateperiodically removing and replacing the hydrocarbon absorbing sheet 144without necessitating removal of the mass airflow sensor 180 from thehousing 136. In some embodiments, however, any of various suitably sizedopenings may be disposed in the duct 140 and hydrocarbon absorbing sheet144, in lieu of the channel 184 and separation 188, and configured toreceive the mass airflow sensor 180.

As best shown in FIGS. 5 and 6 , the duct 140 comprises at least a pairof guide vanes 192 that extend across an interior of the duct andadjacent to the mass airflow sensor 180. The guide vanes 192 areconfigured to advantageously reduce air turbulence within the airstream116 passing by the mass airflow sensor 180 during operation of theengine. It is contemplated that reducing turbulence of the airstream 116passing by the mass airflow sensor 180 may provide relatively greateraccuracy of air flow measurements. As shown in FIGS. 6 and 6A, the massairflow sensor 180 may be disposed between the guide vanes 192 so as toencourage a substantially laminar flow of the airstream 116 on bothsides of the mass airflow sensor. In some embodiments, the guide vanes192 may be molded as a portion of the duct 140, or the guide vanes 192may comprise separate components that may be coupled with the duct 140,without limitation. It is contemplated that any of various structuresmay be implemented, in lieu of the guide vanes 192, as may be found toadvantageously reduce turbulence in the airstream 116, withoutlimitation.

While the invention has been described in terms of particular variationsand illustrative figures, those of ordinary skill in the art willrecognize that the invention is not limited to the variations or figuresdescribed. In addition, where methods and steps described above indicatecertain events occurring in certain order, those of ordinary skill inthe art will recognize that the ordering of certain steps may bemodified and that such modifications are in accordance with thevariations of the invention. Additionally, certain of the steps may beperformed concurrently in a parallel process when possible, as well asperformed sequentially as described above. To the extent there arevariations of the invention, which are within the spirit of thedisclosure or equivalent to the inventions found in the claims, it isthe intent that this patent will cover those variations as well.Therefore, the present disclosure is to be understood as not limited bythe specific embodiments described herein, but only by scope of theappended claims.

What is claimed is:
 1. A hydrocarbon trap for absorbing evaporativehydrocarbon emissions from an air intake duct of an internal combustionengine, the hydrocarbon trap comprising: a duct configured tocommunicate an airstream from an air filter to the air intake duct; amultiplicity of ports disposed along the duct to allow evaporativehydrocarbon emissions to be drawn from the air intake duct; a housingconfigured to support the duct and at least one hydrocarbon absorbingsheet to arrest the evaporative hydrocarbon emissions; and a port in thehousing configured to support a mass airflow sensor within the duct. 2.The hydrocarbon trap of claim 1, wherein the duct is coupled with atleast one support configured to maintain the hydrocarbon absorbing sheetin an unfolded configuration adjacent to an inner perimeter surface ofthe housing.
 3. The hydrocarbon trap of claim 2, wherein the at leastone support is configured with a shape that matches the shape of theinterior and a size that provides clearance for the hydrocarbonabsorbing sheet to be disposed between the edges of the at least onesupport and the inner perimeter surface.
 4. The hydrocarbon trap ofclaim 1, wherein the housing is configured to be coupled with an air boxso as to communicate the airstream through the duct during operation ofthe internal combustion engine.
 5. The hydrocarbon trap of claim 4,wherein the housing comprises a mounting surface that is configured tomate with a substantially similar surface disposed on the air box. 6.The hydrocarbon trap of claim 5, wherein one or more holes disposed inthe mounting surface are configured to receive fasteners for couplingthe housing to the air box.
 7. The hydrocarbon trap of claim 1, whereinthe port is configured to extend the mass airflow sensor into theairstream within the duct during operation of the internal combustionengine.
 8. The hydrocarbon trap of claim 7, wherein the duct includes achannel that is configured to receive the mass airflow sensor when theduct is installed into the housing.
 9. The hydrocarbon trap of claim 8,wherein the hydrocarbon absorbing sheet includes a separation configuredto receive the mass airflow sensor when the duct is installed into thehousing.
 10. The hydrocarbon trap of claim 1, wherein at least one guidevane extends across an interior of the duct adjacent to the mass airflowsensor and is configured to reduce air turbulence within the airstreampassing through the duct during operation of the internal combustionengine.
 11. The hydrocarbon trap of claim 10, wherein the at least oneguide vane comprises two guide vanes disposed on opposite sides of themass airflow sensor and configured to encourage a substantially laminarflow of the airstream on both sides of the mass airflow sensor.
 12. Ahydrocarbon trap for absorbing evaporative hydrocarbon emissions from anair intake duct of an internal combustion engine, the hydrocarbon trapcomprising: a housing coupled with an air filter; a duct disposed withinthe housing to communicate an airstream from the air filter to the airintake duct; a hydrocarbon absorbing sheet disposed between the duct andthe housing; and a mass airflow sensor disposed within the airstream.13. The hydrocarbon trap of claim 12, wherein the duct is comprised ofat least one support configured to maintain the hydrocarbon absorbingsheet in an unfolded configuration adjacent to an inner perimetersurface of the housing.
 14. The hydrocarbon trap of claim 12, wherein amultiplicity of ports disposed along the duct are configured to allowthe evaporative hydrocarbon emissions to be drawn from the air intakeduct into the housing.
 15. The hydrocarbon trap of claim 12, wherein thehousing comprises a port configured to extend the mass airflow sensorinto the duct.
 16. The hydrocarbon trap of claim 12, wherein at leasttwo guide vanes extend across the duct adjacent to the mass airflowsensor and are configured to reduce air turbulence within the airstreampassing by the mass airflow sensor during operation of the internalcombustion engine.
 17. The hydrocarbon trap of claim 16, wherein themass airflow sensor is disposed between the at least two guide vanes,such that the airstream is substantially laminar on both sides of themass airflow sensor.
 18. The hydrocarbon trap of claim 12, wherein thehousing is configured to be coupled with an air box that contains theair filter, such that the airstream is communicated from the air filterto the air intake duct.
 19. A hydrocarbon trap for absorbing evaporativehydrocarbon emissions from an air intake duct of an internal combustionengine, the hydrocarbon trap comprising: a duct configured tocommunicate an airstream from an air filter to the air intake duct; ahousing configured to support the duct and at least one hydrocarbonabsorbing sheet within an interior of the housing; one or more supportscoupled with the duct and configured to maintain the hydrocarbonabsorbing sheet in an unfolded configuration within the housing; and amultiplicity of ports disposed along the duct and configured to allowthe evaporative hydrocarbon emissions to be drawn from the duct andarrested by the hydrocarbon absorbing sheet.
 20. The hydrocarbon trap ofclaim 19, wherein the housing is configured to be coupled with an airbox that at least partially surrounds the air filter, such that theairstream is communicated into the duct during operation of the internalcombustion engine.
 21. The hydrocarbon trap of claim 19, wherein thehousing comprises a port configured to receive a mass airflow sensorinto the duct, such that the mass airflow sensor is exposed to theairstream.